问题 问答题 论述题

循环氢纯度高、低说明什么问题?

答案

参考答案:

氢纯度表示脱氢反应程度和催化剂选择性变化情况。催化剂选择性〔脱氢活性)越好氢纯度就越高,温降也越大。反之,氢纯度下降,循环气中烃类气体含量增加,表明裂化反应加剧,催化剂选择性变坏,液体产品收率将会下降,这时,如果其它条件未变,应着重检查系统的水氯平衡是否失调,当然如果催化剂中毒失活,氢纯度也会下降,也应从这方面检查。总之,分析循环氢纯度有助于了解反应程度,给调整操作提供依据,对平稳操作是很重要的。

阅读理解

阅读理解。

     When I was seven years old, my family made me an ant farm. First, we put clean sand in a thin glass

box. Then we waited for the ants to arrive.

     After the ants were in the glass farm, they started to make tunnels. I was very surprised that each one

knew exactly what to do. Each had its own job.

On the fifth day a tragedy (悲剧) happened. I put my face so close to the glass farm that I knocked it

over. All the tunnels fell down. Although the ants remained alive after the earthquake, one by one they

began to die. I was scared as I watched them give up building their tunnels to carry bodies to a corner

of the farm.

My mother said that the ants were dying of sadness. They simply could not understand why their tunnels

were gone.

     Although much time has passed, I still think of that ant farm. Mom had hoped it would teach me about

the natural world, but it taught me much more.

Over the years, I came to realize the importance of teamwork. Working together, the ants were able to

make an amazing world for themselves. I also learned that they should be admired for their hard work.

     But there was an even larger lesson that I did not realize until recently: Adversity (逆境) is a natural

part of life, and must be accepted. Unlike the ants, we cannot give up when we are sad. We have to

realize that if a tunnel is gone, we must build another.

Giving up, I say, is not a good choice.

1. What did the writer's family do for him when he was seven?

A. They built a farm of ants.              

B. They bought a few ants.

C. They caught a lot of ants.              

D. They found an ant city.

2. Which is the correct order of the following?

a. All the tunnels fell down.          

b. The ants died one by one.

c. The ants got into the glass box.    

d. The ants began making tunnels.

A. a-b-c-d        

B. a-c-d-b          

C. c-d-a-b        

D. c-a-d-b

3. What did the writer come to realize a few years later?

A. Working together is useless.        

B. Teamwork is important.

C. He can't accept adversity.          

D. Working alone is amazing.

4. What is the best title for the passage?

A. Ants Fear Adversity              

B. My Family and Ant

C. Giving up in Adversity            

D. A Good Lesson from Ant

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